My last long paved road tour (Southern Tier) I went with a 39/26 and a 12-28 (a range of about 25-48 gear inches) carrying 14 pounds base gear weight and was very happy with the choice. The 39/26 was a triple with the big ring left off.
Since then I have spent quite a bit of time on a 2x10 mountain bike and based on my experience with that setup I might go with either a 1x10 or a 2x10 if I were setting up a touring bike from scratch. I think I'd actually favor the 1X10 (or maybe even a 1x11)
Some of the new MTB clusters are really super wide range. Enough so that a 1x10 really can work fine for just about any road conditions. I think that if I were starting from scratch I'd consider a 1x10 with an 11-42 MTB cluster and what ever ring gave me the low gear I wanted.
All that said... In your case I'd probably just go to a MTB double and stick with the 12-32 unless your current crank can take appropriate sized rings. I'd err on the side of closer spaced rings and accept a lower high gear. How low would depend on the load and the terrain. At 60 pounds of gear, in the mountains you will likely need to go lower than I normally would with my lighter load.